Mapping as methodology
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* Erica Weir

Disease Maps:Epidemics on the Ground.  Tom Koch. University of Chicago Press; 2011.

It is almost impossible to attend a public health conference in Canada nowadays without some mention in the proceedings about the “built environment.” Study within this emerging :field looks at the interrelationship between urban design and its impact on sustainable, healthy living. Mapping the proximity of fast-food outlets to neighbourhood clusters of diabetes is one illustration of an exploratory study under this theme. Although the data produce products from digitalized geospatial analysis about the association between urban environmental features and chronic disease rates that may be relatively new, any delusion that mapping as a methodology is similarly new is quickly dispelled by Koch’s foundational book, *Disease Maps: Epidemics on the Ground*. Maps have informed public health theory, investigations, understanding and political decisions for centuries.

![Figure1](http://www.cmaj.ca/https://www.cmaj.ca/content/cmaj/184/9/1067/F1.medium.gif)

[Figure1](http://www.cmaj.ca/content/184/9/1067/F1)

Image courtesy of University of Chicago Press

Koch’s stately text develops and illustrates the argument that mapping the spatial relationships between disease and posited environmental influences is a methodology. As such, maps carry the exciting potential to identify and establish new empirical associations, yet they are susceptible to the same limitations of data accuracy and investigator biases as any other methodology — maybe even more so given our inherent tendency to conform visual information to known patterns. Readers forewarned: this can be especially concerning in the arena of public health when the backdrop to spatial patterns may be outlined by pre-existing political boundaries.

The author guides the reader through the maturation and exposition of disease mapping as a methodology in a series of 12 chapters divided into three sections, each supported by an impressive collection of archival maps and illustrations. The first section introduces the concept of cartographies of disease and documents the epistemology of the spatial classification of disease symptoms and origins. Advancements in the history of medicine, such as Vesalius’ use of experiential knowledge to draw anatomy, align with developments in cartography, such as the insertion of longitude and latitude as spatial reference points to refine maps as tools of enquiry and empirical workbenches.

In the second section, the author invites the reader closer to the workbench, using cholera as the exemplar. Through critical review, assimilation and even secondary analysis of a century’s worth of epidemiological data, maps and theories, Koch documents the range of mapping experiments conducted by scientists, physicians, bureaucrats and theologians as they strove to explain and control the local outbreaks of cholera that exacted a pandemic toll. He debunks the notion that John Snow was the singular hero who cracked the case by removing the handle from the Broad Street pump and rightly repositions the complexity of scientific investigation back within its broad and dissenting community.

The third section briefly features cancer as the new cholera and opens the door for innovative mapping techniques to explore the geospatial attributes of chronic diseases that today’s studies offer about the built environment.

This is a gravid, heavy book about the often overlooked, yet extremely important spatial dimension of disease relationships. It merits slow pondering and deliberate thought, enhanced perhaps by a dictionary to look up the origins and meanings of certain words — eccentric, malaria and constantive — and a magnifying glass to zoom in on certain points in the illustrated maps not apparent to the onlookers on first inspection, particularly when they are biased.